San Mateo to convert its waste into fuel: City first to turn biogas into compressed natural gas at wastewater plant

Posted December 11, 2015,  By Samantha Weigel in the Daily Journal

Most might not consider that flushing a toilet or running a dishwasher could contribute to fueling a vehicle. But such is the future for thousands of local residents, as San Mateo will break ground on California’s first city-run biogas conversion project to produce compressed natural gas at its wastewater treatment plant.

This $5 million improvement will contribute to the city’s sustainability goals by reducing its dependency on gasoline thereby reducing greenhouse gas emissions.

After receiving a $2.45 million grant from the state, the city plans to construct a digester that will capture underutilized biogas, which naturally occurs while treating wastewater, and turn it into compressed natural gas that will be used to fuel new city-owned vehicles.

San Mateo is the first city in the state to use this advanced technology at a wastewater treatment plant, allowing it to produce the biofuel equivalent of 500 gallons of gasoline every day.

“It takes gas created from the wastewater treatment plant process and it will convert it through cleansing then compressing that gas into compressed natural gas that can be used in vehicles,” said Public Works Director Brad Underwood. “It’s exciting to be on the leading edge in California for this. We hope it’ll turn into a great success and that others can then utilize and build off of and convert their own digester gas to help other aspects in their department and city.”

Anticipating completion in August, the project includes a distribution system that serves like a pump at a traditional gas station, Underwood said.

Typically, the plant just burns off the biogas that’s created as part of the treatment process at the facility that accepts wastewater from San Mateo, Foster City, Hillsborough, Belmont and unincorporated portions of the county.

Although the current flare of gas burning off 24/7 will not completely cease since the digester cannot convert all of the excess, it will be significantly reduced, Underwood said.

Furthermore, by purchasing at least 50 new clean natural gas vehicles — likely pickup trucks for the Public Works as well as Parks and Recreation departments — the city will become less reliant on traditional fuel. As vehicles are the number one contributor to the city’s greenhouse gas emissions, this project supports long-term environmental initiatives.

“It’s definitely part of our Climate Action Plan and sustainability goals to switch from gas engines and diesel engines to alternative fuels. The effect of using the byproduct is we can utilize it instead of burning it off or essentially wasting it,” Underwood said.

The plant will be producing nearly 160,000 diesel gallon equivalents of biofuel each year, more than the initial fleet of new vehicles can use. Eventually, the city will likely expand its fleet and may consider selling the gas to anyone with compressed natural gas vehicles — either individuals or other cities. The city may also consider finding other ways to use the cleaner burning gas within plant operations, such as to fuel the boiler, Underwood said.

With the nearly $2.5 million grant from the California Energy Commission, this breakthrough and exciting project has tremendous financial as well as environmental benefits, said Mayor Joe Goethals.

“It really adds up in terms of carbon reductions that the city gets from this. It’s carbon that would otherwise just be admitted into the atmosphere and instead we’re using it to offset the gasoline that our fleet would otherwise use. So it’s a very exciting project and we’re glad to be the model for the state on this,” Goethals said. “I think we’re going to see wastewater treatment plants converting to this, because it’s not only good for the environment, it’s good for our budget.”

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Megan Barillo

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